The present invention is directed to an adjustable floating step arrangement for pivotal connection to platforms and the like by which personnel may achieve safe access to the top of various height tank trailers, railway tank cars, hopper cars and other carriers requiring access to their tops.
In loading tanker trucks by manually handling a filling hose, for instance, an operator needs to reach the top of the tank of the truck, usually from a platfrom that may be located at a level higher or lower than the top of the tank of the vehicle concerned or adjacent thereto. When the operator attempts to step from the platform onto the top of the tank, he often finds the tank top to have a curved and smooth surface from which he runs the risk of making a misstep, thus possibly slipping and falling to the ground. The risk is significantly increased during inclement weather, as during rain, snow, sleet and freezing weather.
U.S. Pat. No. 4,013,140 discloses one form of step construction by which an operator may obtain access from a platform to the top of vehicles of various heights, such as tanker trucks at hydrocarbon loading stations. The patent discloses a flight of steps, which at one end is pivotally connected to a platform and at the other end is adapted to be moved into contact with and to be supported by the top of the vehicle. The treads of the steps disclosed remain horizontal irrespective of the inclination of the steps by means of a parallelogram linkage. In constructions of the type represented by this patented disclosure, the multiple linkages shown connecting the individual steps in time tend to become rusted due to their exposure to the weather and thus the steps become less freely movable. This construction requires more maintenance to maintain free movement and to preclude or minimize rusting. Although tank tops are fairly sturdy, they can be damaged or punctured if through carelessness or accident the movement of the steps into contact with the tank top should be too fast or the operator should attempt to walk down the steps while the steps have not yet contacted the tank top and the weight of the operator suddenly forces the steps into sudden contact with the tank top.
U.S. Pat. No. 4,013,140 discloses a collapsible step arrangement which may serve as a stairway or step ladder and which also employs a parallel linkage arrangement by which the steps may remain horizontal when in the opened position. This patent also discloses a latching arrangement by which the steps and parallel linkages may be locked in the closed or collapsed position to prevent unintended reopening of the step arrangement.
U.S. Pat. No. 2,498,375 discloses an adjustable ladder employing a parallel linkage arrangement in which cams are used to lock the pivotal steps so that the steps will remain level at the desired adjusted inclination of the ladder.
An object of the invention is to provide a safety floating step assembly by which an operator may have safe access from a platform to the top of the tanks of trucks and the like, the safety floating step assembly being self-supporting and independent of support by and or engagement with the top of such tanks.
Another object of the invention is to provide a safety floating step assembly havng a single pair of spaced apart side-by-side parallel four-bar linkages for supporting a step assembly by which an operator may obtain safe access to the top of tanks from a platform or the like, and which has relatively few moving parts requiring maintenance.
Still another object of the invention is to provide a safety floating step assembly, which is pivotally connected to and from a platform or the like and is provided with a locking arrangement at the location of the pivot for releasably locking the floating step assembly at different positions relative to the height of the tank of the vehicle positioned alongside the platform or other carrier.
Other objects of the invention will become apparent to those skilled in the art to which this invention pertains when reading the disclosure that follows.